JPS608618A - Gas combustion controller - Google Patents

Abstract

PURPOSE:To set an air ratio to a low value over a wide combustion range, by a method wherein a variable throttle mechanism is situated between the upper stream side of an air throttle and the throat part of a mixture part in the shape of a venturi pipe, and a blower and the variable throttle mechanism are controlled through detecting of a difference in a pressure between the upper stream sides of a gas throttle and the air throttle. CONSTITUTION:A gas amount regulating means 2 and a gas throttle 3 are located on a gas side passage 1, and a blower 5 and an air throttle 6 are positioned on an air side passage 4. After the air for combustion is joined at a venturi pipe-shaped mixture part 7, it is guided to a burner 9 through a mixture gas passage 8. A differential pressure sensor 10 detects the difference in the pressure between the upper stream sides of the gas throttle 3 and the air throttle 6. In a range of from a maximum combustion amount to a given combustion amount, a control part 15 variably controls the blower 5 in a condition in which a variable throttle mechanism 13 is held in a full closed state, and the blower 5 is controlled so as to hold at a specified amount of the air answering to a give combustion amount and the variable throttle mechanism 13 is variably controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a combustion control device that variably controls the combustion amount of a combustion device.

Conventional configuration and its problems A conventional combustion control device is shown in FIG.

A gas amount control valve 3 is provided on the upstream side of the gas throttle 1, the gas differential pressure sensor 1a, the air throttle 2, and the air differential pressure sensor 2a, respectively.
, a combustion air supply means 4 is provided, and the downstream sides of the two throttle portions merge and are led to the combustion chamber 5. θ is a control unit that controls the gas amount control valve 3 or the combustion air supply means 4 according to the external load or the output of the differential pressure sensor to variably control the combustion amount according to the load.

In FIG. 1, Pq is the outlet side pressure of the gas amount control valve 3;
That is, it is the upstream pressure of the gas throttle 1. Pa is the outlet pressure of the combustion air supply means 4, that is, the upstream pressure of the air restrictor 2. Pm is the pressure at the junction of fuel gas and combustion air. In the above configuration, when the fuel gas flow rate Qq and the combustion air flow rate Q are expressed using the pressures of Pg, Pa, and Pm, it becomes Q9=K1dotomi1o,=x24. However, K1. 2 is the constant of proportionality.

The theoretical air amount QaO is 3 to Qao- with K3 as a constant.
Qg= can be expressed as 34 (1S〒=.

Therefore, if the air ratio is expressed as m, m= Qa/Qao= (K2 J ()/(K3・K
If we set K4- to 2/3 to K1, the control unit 6 has the function of changing the combustion amount in response to the external load and controlling the air ratio at the same time, as briefly explained above. The method of air ratio control always has P a =
P g, that is, 2 4 FT 7 Yo 5
This is to make it so that 4 (constant) = 4 (constant). However, the differential pressure sensor has a certain error e due to variations in output, and in reality, it does not become Pa `` P s but Pa - Pg 10, so the actual value of the air ratio m is = 4, 17th edition of Kaorishi.

In other words, the air ratio m is a function of (Pg-Pm).

FIG. 2 illustrates this situation with (Pg-Pm), ie, gas flow rate 0 g, plotted on the horizontal axis and air ratio m plotted on the vertical axis.

Since the fuel gas flow rate, that is, the combustion amount, is proportional to n, the left side of FIG. 2 indicates the low combustion region. As is clear from the figure, for a constant error of 10, the error in the air ratio m suddenly increases in the low combustion range.

FIG. 3 shows both the range of good combustion indicated by rough hatching and the range of variation in the air ratio m described above superimposed on a coordinate plane having the same axis as in FIG. 2. The lower limit of the range for good combustion depends on the combustion characteristics of the burner, but is generally approximately constant at about 1.2 to 14.

As is clear from the figure, the limit value of the dispersion of the air ratio m spreads rapidly in the low combustion range, so it is necessary to set the air ratio m to a high value, that is, m==1+A. On the other hand, if the air ratio m is set as small as possible, the error in the air ratio m will rapidly increase in the low combustion range, which will deviate from the lower limit of the good combustion range. need to be narrowed down.

Therefore, under such conditions, extra combustion air is always supplied in areas other than the low combustion range, which increases the amount of heat carried away by the exhaust gas and causes a decrease in thermal efficiency. Ta. However, in order to supply surplus combustion air, the combustion air supply means such as a blower became larger, which also led to an increase in combustion noise.

Purpose of the Invention The present invention solves these conventional problems.
The purpose of this is to prevent the lower limit curve of air ratio variation from rapidly expanding downward, especially in the low combustion range, to set the air ratio to a low value over a wide combustion range, and to improve wind resistance. It was measured.

Structure of the Invention In order to achieve this object, the present invention provides a gas amount adjusting means and a gas throttle in the gas side passage, and a blower for supplying combustion air and an air throttle in the air side passage. The downstream sides of each are joined at a venturi tube shaped mixing section and guided to the burner, and the upstream side of the air throttle and the bench 9 are connected to each other.
- A bypass passage provided with a variable throttle mechanism between the throat part of the tube-shaped mixing part, and a differential pressure detection means for detecting a pressure difference on the upstream side of each of the gas throttle and the air throttle, and the blower and the A control section is provided to control the variable diaphragm mechanism.

With this configuration, in a region where the combustion amount is above a predetermined value, the air ratio remains constant even if the combustion amount changes in response to the burner load (however, assuming that the error of the differential pressure detection means is zero). The air ratio can be controlled by changing the air ratio in a region below a predetermined value.

Therefore, it is possible to increase the air ratio in the region where the combustion amount is below a predetermined value and prevent the lower limit curve of the air ratio variation from rapidly expanding downward. It is possible to have the effect that the ratio does not go below the lower limit curve of the good combustion range.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 4 to 7.

In FIG. 4, a gas amount adjusting means 2 and a gas throttle 3 are provided in the gas side passage 1, and a blower 5 and an air throttle 6 are provided in the air side passage 4. After the gas and the combustion air are combined in a Pencilly tube-shaped mixing section 7, they pass through a mixed gas passage 8 and are led to a burner 9. 10 is differential pressure detection means such as a differential pressure sensor that detects the pressure difference on the upstream side of the gas throttle 3 and the air throttle 6 (hereinafter the differential pressure detection means will be referred to as a differential pressure sensor);
Reference numeral 1 designates a differential pressure sensor detection circuit, reference numeral 12 designates a bypass passage that communicates the upstream side of the air throttle 6 with the throat portion of the Venturi tube-shaped mixing section 7, and reference numeral 13 designates a variable throttle mechanism disposed in the bypass passage 12. and 14 is a secondary air passage, 15
In the range from the maximum combustion amount to a predetermined combustion amount, the blower 5 is variably controlled with the variable throttle mechanism 13 kept fully closed;
Further, in a region where the combustion amount is less than a predetermined combustion amount, the control unit is configured to control the blower 6 to maintain a constant air amount corresponding to the predetermined combustion amount, and to variably control the variable throttle mechanism 13. be. 16 is a temperature setting device, and 17 is a temperature detection circuit.

In the above configuration, it is assumed that the maximum rated combustion amount is currently reached. In such a state, the temperature setting device 16
When the hot water temperature is reset to a lower value, that is, when the load is reduced, the temperature setting device 16
The deviation signal from the temperature detection circuit 17 is processed by the control unit 16, and the blower 5 is controlled to reduce the amount of air. Therefore, when the air amount decreases, a differential pressure is generated in the differential pressure detection means 1o, and this differential pressure output is processed by the differential pressure sensor detection circuit 11, and the gas amount adjustment means 2 is adjusted so that the differential pressure output becomes zero. Control so that the gas amount decreases. Further, if the load is increased from such a state, the air amount and gas amount are controlled to increase. That is, even if the load fluctuates, the gas amount changes to follow the air amount, so the air ratio m is maintained at a substantially constant value. In this state, the predetermined combustion amount (for example, the value of % of the maximum rated combustion amount) is still set.
has not decreased to.

In this state, the variable diaphragm mechanism 13 is held in a fully closed state by the control section 16.

Next, from this state, the load is further reduced by /h,
In an area where the combustion amount is less than a predetermined combustion amount (for example, in the range from a value of % of the maximum rated combustion amount to a value of the minimum combustion amount), the amount of air sent out by the blower 5 built in the control unit 15 (% of the maximum rated combustion amount) At the same time that the circuit that maintains the air amount at a constant value operates, the variable diaphragm mechanism 13 is variably controlled by the deviation signal from the temperature setting device 16 and the temperature detection circuit 17.

In order to make the above operation easier to understand, Fig. 6 shows the changes in the air-fuel ratio assuming that the error in the control system such as the differential pressure sensor 10° and the differential pressure sensor detection circuit 11 is assumed to be zero. FIG. 6 shows the relationship between the amount of combustion (gas amount QG) and the air ratio m. Next, we will consider the actual case where control system errors occur in the differential pressure sensor 10, etc. within the range of good combustion determined by the combustion characteristics of the burner 9, that is, the change situation of the air ratio m taking into account control system variations. What is shown is FIG. In addition, in FIGS. 5 to 7, a, b,
c indicates the maximum rated combustion amount, the predetermined combustion amount, and the minimum combustion amount, respectively. In addition, A and A in FIG. 7 represent the upper and lower limits of the good combustion range, respectively.

In the above configuration, if the air ratio m at the maximum rated combustion rate is determined as is clear from FIG. become. However, as in one embodiment of the present invention, by fixing the air amount to the same value as point b and varying only the gas amount from point b to point C, the air ratio m can be increased and the burner 9 can achieve good combustion. By not exceeding the lower limit of the range, the combustion amount variable range can be extended from point b to point C.

Next, another embodiment of the present invention will be described using FIGS. 8 to 10. FIG. 8 is illustrated assuming that the control system error of the differential pressure sensor 10 and the like is zero for ease of understanding.

The difference in FIG. 9 from the above embodiment is that the predetermined combustion amount is divided into two, bl and b2, and the configuration can control the air ratio m from the predetermined combustion amount b2 to the minimum combustion amount C while keeping the air ratio m constant. This is what I did. That is, when the variable diaphragm mechanism 13 is fully opened at b2, it is held fully open to the 0 point, and the control unit 15 is configured so that the deviation signal from the temperature setting device 16 and the temperature detection circuit in turn controls the blower 5. It is.

According to this configuration, the upper limit of the range of good combustion determined by the combustibility of the burner is horizontal in the vicinity of a low combustion amount, and it is extremely useful as a control means when the air ratio m is required to be a constant value in this vicinity. Effective. FIG. 10 shows this relationship in an actual case where there is an error in the control system of the differential pressure sensor 1o, etc.

Note that C and C in FIG. 10 represent the upper and lower limits of the good combustion range, respectively.

Effects of the Invention As is clear from the above explanation, the gas combustion control device of the present invention provides the following effects.

(1) A differential pressure detection means is installed to detect the difference between the pressure between the gas amount adjustment means and the gas throttle and the pressure between the blower and the air throttle, and the downstream sides of each are merged at the Pencilley tube-shaped mixing section. a control unit that connects the upstream side of the air throttle and the throat of the ventilly tube-shaped mixing unit through a bypass passage having a variable throttle mechanism therebetween, and controls the blower and the variable throttle mechanism; By being equipped with this, when the amount of air changes in response to load fluctuations in a region where the amount of combustion is greater than a predetermined value, the differential pressure detection means operates the gas amount adjustment means so that the differential pressure becomes zero (or a predetermined value). Therefore, the air ratio can be controlled at a constant level. In addition, when the combustion amount falls below a predetermined value, the amount of air blown by the blower becomes a constant value, and the variable throttling mechanism operates in response to load fluctuations, so the air ratio is set as low as possible. The combustion amount variable range can be expanded by Therefore, it is possible to realize a combustion device with high thermal efficiency and low combustion noise.

(2) In the region of low combustion amount, the air ratio is controlled to increase without depending on the positive or negative fixed error of the differential pressure detection means, so there is an advantage that the wind resistance performance of the combustion equipment can be improved. (3) Furthermore, by configuring the control unit to hold the variable throttle mechanism fully open and operate the blower according to load fluctuations,
It is also possible to control the air ratio to be constant, so even if the combustion characteristics (range of good combustion) of the burner are complex, the air ratio can be controlled in accordance with the combustion characteristics. It is something.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a conventional combustion control device, FIGS. 2 and 3 are explanatory diagrams of the same operation, FIG. 4 is a configuration diagram showing an embodiment of the gas combustion control device of the present invention, and FIGS. Fig. 6 is a control characteristic diagram when there is no error in the control system such as the differential pressure detection means, and Fig. 7 is a control characteristic and burner combustion characteristic in an actual case where there is an error in the control system such as the differential pressure detection means. Figures 8 and 9 are control characteristic diagrams in the case where there is no error in the control system such as the differential pressure detection means in the second embodiment of the present invention, and Figure 10 is a diagram showing the actual control characteristics with errors. It is a figure which shows the relationship between the control characteristic and the combustion characteristic of a burner in case. 1...Gas side passage, 2...Gas amount adjustment means, 3...Gas throttle, 4...Air side passage, 5
...Blower, 6...Air throttle, 7...Bentley tube shape mixing section, 9...Burner, 1o...
Differential pressure detection means, 12... Viper passage, 1
3...Variable aperture mechanism, 16...Control unit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 1m / Vaporization Figure 4 Figure 5

Claims (1)

[Claims] (1) A gas amount adjusting means and a gas restrictor are installed in the gas side passage, and a blower and an air restrictor are installed in the air side passage to supply combustion air, and the downstream side of each is provided with a Venturi pipe. a bypass passage that merges at the shape mixing section and leads to the burner, and in which a variable throttle mechanism is inserted between the upstream side of the air throttle and the throat section of the venturi tube shape mixing section;
The device further comprises differential pressure detection means for detecting a pressure difference between the pressure between the gas amount adjusting means and the gas throttle and the pressure between the blower and the air throttle, and further includes a pressure difference detecting means for detecting a pressure difference between the pressure between the gas amount adjusting means and the gas throttle, and further comprising a pressure difference detecting means for detecting a pressure difference between the pressure between the gas amount adjusting means and the gas throttle and the pressure between the blower and the air throttle. In the range above the predetermined value, the variable throttle mechanism is held in a fully closed state to control the combustion air, and in the range below the predetermined value, the combustion air is held at a constant value and the variable throttle mechanism is controlled. A gas combustion control device consisting of a control section that controls a combustion mechanism. 2)) The gas combustion control device according to claim 1, wherein the variable throttle mechanism is configured to be operated by electromagnetic force.